What is Placenta Accreta?
In a normal pregnancy, the placenta, which nourishes the baby, attaches itself to the inner lining of the uterus, known as the endometrium.1 Sometimes, the placenta abnormally burrows itself deeper into the muscular layer of the uterus, known as the myometrium. This condition is called placenta accreta. It can occur at different levels of severity, including placenta accreta, placenta increta, and placenta percreta, which are collectively referred to as placenta accreta spectrum (PAS) disorders.
These disorders can lead to an increased risk of complications during and after delivery. Thus, it is crucial that women with PAS disorders are taken care of by a medical team consisting of different specialists.2 The International Federation of Gynecology and Obstetrics (FIGO), a worldwide organization of women’s health experts, has come up with a classification system for PAS disorders. This system replaces the old way of categorizing these disorders – that is, as placenta accreta, increta, and percreta.3
What Causes Placenta Accreta?
The spectrum of disorders related to the placenta sticking too deeply in the womb (collectively known as Placenta Accreta Spectrum or PAS) is typically linked to a past cesarean section. This likely happens because the surgical scar from the cesarean section disrupts the layer of tissue (decidua) that lines the uterus, which can affect how the placenta attaches. Nevertheless, there are other factors that can increase the risk of placenta accreta, including being older during pregnancy and having given birth multiple times before.
Out of every five women with placenta accreta, four of them have a condition called placenta previa where the placenta covers the opening of the cervix. Additionally, placenta accreta has been associated with other types of surgery on the womb, such as removing fibroids (myomectomy), scraping the uterus lining (uterine curettage), using a thin tube to examine the uterus (hysteroscopic surgery), previously treating heavy periods by destroying the uterus lining (endometrial ablation), blocking the blood vessels in the uterus (uterine embolization), and having radiation therapy in the pelvic area.
Risk Factors and Frequency for Placenta Accreta
The rate of placenta accreta, a pregnancy complication, has increased significantly over the years. In the 1960s, it was 1 in 30,000 pregnancies but in the 2000s, it increased to 1 in 533 pregnancies. Some studies even show it is currently as high as 1 in 272 pregnancies.
This condition is closely related to having a history of cesarean deliveries. So, the rise in placenta accreta cases is partly because of the increase in cesarean deliveries over the years. In fact, the more cesarean sections a woman has had, the higher her risk of developing placenta accreta. For example, about 6.7% of women with five previous c-sections have developed this condition compared to just 0.3% among women with only one c-section in their past.
Signs and Symptoms of Placenta Accreta
The first pregnancy check-up is very important because it allows doctors to identify things that may increase the risk of placenta accreta, a condition where the placenta attaches too deeply into the wall of the womb. This can include a woman’s pregnancy history and any past surgeries she’s had on her uterus. Generally, a diagnosis is made through medical imaging procedures. It’s rare, but sometimes, when the condition involves the bowel and urine systems (a case known as placental percreta), a woman may experience bowel and urinary problems.
Testing for Placenta Accreta
When a pregnant woman has a condition known as placenta accreta, it’s usually identified through an ultrasound. This is a condition where the placenta grows too deeply into the uterine wall. An ultrasound is a medical imaging method that uses high-frequency sound waves to create images of the inside of the body. In this case, it shows the placenta being in an abnormal position, known as placenta previa. The ultrasound scan can also display other issues like a missing clear division between the placenta and myometrium (muscular layer of the uterus), increased blood vessels, thinning of the myometrium, and the placenta extending into the serosa (the lining of the uterus) or bladder.
A particular type of ultrasound called Color Doppler may show irregular blood flow in spaces within the placenta, known as lacunae. However, the effectiveness of ultrasound in diagnosing placenta accreta can vary quite a bit. Some studies show a vast range in how accurate it is at detecting this condition. However, according to a thorough review and analysis of many studies, ultrasound had a 90.8% sensitivity (ability to correctly identify those with the condition) and a 96.9% specificity (ability to accurately identify those without the condition). Important factors in the diagnosis include the presence of lacunae and missing hypoechoic (less bright) area behind the placenta. Additionally, the presence of placenta previa increases the diagnosis rate from 6.9% to 72.3%. The skill and experience of the person performing the ultrasound also plays a critical role.
Magnetic resonance imaging (MRI), a type of imaging that uses strong magnetic fields and radio waves to create detailed images of the inside of the body, has also been explored as a tool for diagnosing placenta accreta. A comprehensive review of studies using MRI for this purpose indicated a specificity of 84.0% and a sensitivity of 94.4%. While these statistics may seem appealing, it’s important to remember that there can be a selection bias in these studies – meaning an MRI is usually only used when the ultrasound results aren’t clear. It’s also necessary to take into account the costs and sometimes the limited availability of MRIs. As of now, doctors prefer to use ultrasound for diagnosing placenta accreta.
Treatment Options for Placenta Accreta
Placenta accreta is a condition that occurs when the placenta – the organ that provides nutrients and oxygen to the baby during pregnancy – attaches too deeply into the uterine wall. It’s considered a high-risk pregnancy complication and the best management for it is early diagnosis before the baby is born. Many precautions can be taken to minimize risks associated with this condition.
The American College of Obstetricians and Gynecologists (ACOG) suggests that the baby be delivered via cesarean section (C-section) between 34 and 35 weeks of pregnancy. This timeframe is chosen to ensure the baby’s development while reducing the mother’s probability of heavy bleeding. Pregnant women diagnosed with placenta accreta should consider giving birth at specialized health facilities known as Placenta Accreta Centers of Excellence (PACE) or level 3 or 4 care units. These facilities have large, multidisciplinary teams of experts, including high-risk pregnancy specialists, surgeons, intensive care experts, neonatologists, urologists, and other professionals to ensure the best possible care for mother and baby.
C-sections in these cases are typically performed to allow easy conversion to a hysterectomy if needed. A hysterectomy involves the removal of the uterus. After the baby is born, if the placenta does not separate from the uterus on its own, the doctors may decide to leave the placenta inside and perform a hysterectomy to minimize the risk of bleeding.
It’s important to watch the mother’s blood levels and heart function closely during this process. The ACOG also advises on the use of a medication called tranexamic acid within the first three hours after the baby’s birth if necessary. This medication helps reduce the risk of death due to heavy bleeding. Following the procedure, the mother is typically admitted to the intensive care unit (ICU) for careful monitoring of any signs of blood loss, reduced blood flow, or excessive fluid build-up from the administering of fluid treatments.
In some cases, a delayed hysterectomy might be considered. This is when the placenta is left inside the uterus and the hysterectomy is done at a later date. Although still being researched, this method has been shown to decrease blood loss and the need for blood transfusions.
If placenta accreta is discovered unexpectedly during delivery, the procedure should be paused until an experienced team is available and blood products are ordered, and the anesthetic team is informed. If the placenta doesn’t deliver naturally post-birth, an immediate hysterectomy should be considered. If this isn’t possible at the current facility, a transfer should be made to a suitable one.
For women who wish to retain their fertility, they could consider conservative or expectant management. Conservative management involves removal of the placenta or the placenta-uterus tissue without removing the uterus. Expectant management involves leaving the placenta in the uterus (in situ), which, in one study, helped 78% of patients avoid a hysterectomy. Despite these options, it’s crucial to discuss potential risks extensively with the patient, including the risk of hemorrhage, need for a future hysterectomy, and 15%-30% chance of recurrence in future pregnancies.
What else can Placenta Accreta be?
It’s critical to tell the difference between three conditions that are all related to the placenta, namely placenta accreta, increta, and percreta. Knowing whether other organs are involved or not is particularly important before performing planned surgery. Furthermore, it’s important to differentiate between placenta previa and placenta previa accompanied by accreta to ensure proper preparation and advice. The preferred method for imaging in these cases is usually ultrasound, as previously noted, but sometimes an MRI might be used to figure out how far the condition has progressed.
What to expect with Placenta Accreta
The outlook is generally more favorable for patients who have a condition called placenta accreta, without another condition known as placenta previa. When a patient has both placenta accreta and previa, the risk of heavy bleeding and needing to remove the uterus through a procedure called a hysterectomy, both of which can lead to serious health complications, is higher.
Patients who have a condition called placenta percreta face an elevated risk of complications compared to those with placenta accreta and increta. This group of patients has a significantly higher likelihood of injuries to the renal tract (the system in the body that includes the kidneys and the tubes leading to the bladder), needing intensive care unit (ICU) admissions, and requiring additional blood products.
Possible Complications When Diagnosed with Placenta Accreta
The main problem that mothers may face with placenta accreta disorder is excessive bleeding after childbirth. This may lead to low blood flow during the operation, blood transfusion, fluid overload after resuscitation, and a blood clotting disorder called disseminated intravascular coagulation (DIC). In one study, blood transfusion was needed in 80% of cases, and DIC happened in 28% of cases. The best way to lessen the bleeding is to leave the placenta in place after the baby is delivered, but often this is not possible. It is crucial to monitor patients closely in the ICU after surgery to check for any complications related to bleeding.
Another significant risk is injury to nearby organs or structures. Accidental or intentional opening of the urinary bladder can occur during the procedure. The placenta is usually located at the front and may grow into the bladder. In this case, opening the bladder might be necessary to separate the placenta. Damage to the ureters, which carry urine from the kidneys to the bladder, can also happen because of the technical difficulty of performing a hysterectomy during a c-section. It is essential to inform patients about these risks.
The baby can also be affected by these complications. Risks for the baby include premature birth and related problems. Additionally, if the mother bleeds too much, the baby may not get enough oxygen.
Common Complications:
- Excessive bleeding after childbirth
- Low blood flow during the operation
- Blood transfusion
- Fluid overload after resuscitation
- Blood clotting disorder (DIC)
- Injury to nearby organs or structures
- Accidental or intentional opening of the bladder
- Damage to the ureters
- Premature birth
- Decreased oxygen for the baby
Preventing Placenta Accreta
The more cesarean sections (C-sections) a woman has, the higher her risk of developing placenta accreta. Placenta accreta is a serious pregnancy condition where the placenta grows too deeply into the uterine wall. So, if a woman is considering having multiple C-sections or is exploring options for birth control, understanding this risk is crucial.
The possibility of having placenta accreta should be diagnosed as early as possible, and the woman should be made aware of the potential complications. She needs consent to a blood transfusion and needs to know that she might be admitted to the intensive care unit.
The discussion of future fertility is also extremely important. If a woman still wants to have children in the future, she needs to understand the failure rate of fertility-preserving options and the possibility that she might need more surgery.
